#!/bin/bash
# ============================================================================
# DarkForge Linux — Phase 0, Chapter 7: Chroot Environment Setup
# ============================================================================
# Purpose:  Prepare the virtual filesystems and enter the chroot environment.
#           This script must be run as ROOT on the host system. It mounts
#           /dev, /proc, /sys, /run into the LFS tree and enters the chroot.
# Inputs:   LFS environment variable
# Outputs:  Running chroot environment with virtual filesystems mounted
# Assumes:  All Chapter 5+6 scripts (001-022) complete successfully
# Ref:      LFS 13.0 §7.2-7.4
# ============================================================================

set -euo pipefail

LFS="${LFS:-/mnt/darkforge}"

echo "=== DarkForge: Setting up chroot environment ==="

# Verify we're running as root
if [ "$(id -u)" -ne 0 ]; then
    echo "ERROR: This script must be run as root."
    exit 1
fi

# Change ownership from lfs user to root
# (the chroot tools now belong to the system)
chown -R root:root "${LFS}"/{usr,lib,var,etc,bin,sbin,tools} 2>/dev/null || true
case $(uname -m) in
    x86_64) chown -R root:root "${LFS}/lib64" ;;
esac

# --- Create essential directory structure ------------------------------------
mkdir -pv "${LFS}"/{dev,proc,sys,run}
mkdir -pv "${LFS}"/{boot,home,mnt,opt,srv}
mkdir -pv "${LFS}/etc"/{opt,sysconfig}
mkdir -pv "${LFS}/lib/firmware"
mkdir -pv "${LFS}/media"/{floppy,cdrom}
mkdir -pv "${LFS}/usr"/{,local/}{include,src}
mkdir -pv "${LFS}/usr/local"/{bin,lib,sbin}
mkdir -pv "${LFS}/usr"/{,local/}share/{color,dict,doc,info,locale,man}
mkdir -pv "${LFS}/usr"/{,local/}share/{misc,terminfo,zoneinfo}
mkdir -pv "${LFS}/usr"/{,local/}share/man/man{1..8}
mkdir -pv "${LFS}/var"/{cache,local,log,mail,opt,spool}
mkdir -pv "${LFS}/var/lib"/{color,misc,locate}

ln -sfv /run "${LFS}/var/run"
ln -sfv /run/lock "${LFS}/var/lock"

install -dv -m 0750 "${LFS}/root"
install -dv -m 1777 "${LFS}/tmp" "${LFS}/var/tmp"

# --- Mount virtual kernel filesystems ----------------------------------------
# These expose the host kernel's interfaces inside the chroot

# Bind-mount /dev from host (gives us device nodes)
mount -v --bind /dev "${LFS}/dev"

# Mount devpts for pseudo-terminals
mount -vt devpts devpts -o gid=5,mode=0620 "${LFS}/dev/pts"

# Mount /proc (process info filesystem)
mount -vt proc proc "${LFS}/proc"

# Mount /sys (sysfs — kernel objects)
mount -vt sysfs sysfs "${LFS}/sys"

# Mount /run (tmpfs for runtime data)
mount -vt tmpfs tmpfs "${LFS}/run"

# Handle /dev/shm — some systems make it a symlink
if [ -h "${LFS}/dev/shm" ]; then
    install -v -d -m 1777 "${LFS}/$(readlink "${LFS}/dev/shm")"
else
    mount -vt tmpfs -o nosuid,nodev tmpfs "${LFS}/dev/shm"
fi

echo ""
echo "=== Virtual filesystems mounted ==="
echo ""
echo "To enter the chroot, run:"
echo ""
echo "  chroot \"${LFS}\" /usr/bin/env -i   \\"
echo "      HOME=/root                      \\"
echo "      TERM=\"\${TERM}\"                  \\"
echo "      PS1='(darkforge chroot) \\u:\\w\\\$ ' \\"
echo "      PATH=/usr/bin:/usr/sbin         \\"
echo "      MAKEFLAGS=\"-j32\"                \\"
echo "      /bin/bash --login"
echo ""
echo "Then run the chroot build scripts (024-xxx) from inside the chroot."